There are a number of different types of backpacks, totes, duffle bags and luggage units that are used for porting articles from place to place. These prior art portable storage units suffer from a number of shortcomings. For example, once the casing of the portable storage unit is worn out or rips, the entire unit typically needs to be replaced. Also, most soft shell or fabric-type storage units used for travel are structurally flimsy and will collapse, deform or break when placed under a load. Accordingly, such prior art portable storage units can not be stacked or sat upon.
There are also hard shell or solid shell portable storage units. However, like the soft shell portable storage units, they are unusable once the shell is punctured or cracked. Also, the hard shell is typically thin in order to minimize the weight of the portable storage and is, therefore, can collapse when placed under heavy weight. A further shortcoming of a hard shell portable storage unit is that there is no easy way to make a hard shell unit with pockets or other compartments that can be readily accessed from outside the hard shell without opening the main storage compartment formed by the hard shell.
Accordingly there is a need to make a lightweight mobile storage units that are structurally sound, such that they can withstand weight caused by stacking units together and/or sitting on them, without collapsing. Preferably, the mobile storage units have storage compartments that can be replaced in the event of a tear, puncture or other damage. Also, the mobile storage units preferably include outside pockets or other compartments that can be accessed without having to open the main storage compartments of the mobile storage units.